chore(test): set up integration test framework with postgres

- Generate Drizzle migrations (databases/migrations/)
- Add databases/schema.kit.ts for drizzle-kit (Node-compatible imports)
- Update drizzle.config.ts to use schema.kit.ts
- Add deno tasks: test:unit, test:integration, migrate
- Add tests/helpers/db_integration.ts: testDb, truncateAll, seed helpers
- Add .gitea/workflows/test.yml: CI with postgres service container
- Update lint.yml: run test:unit only (no DB needed)
- Update deploy.yml: add check-code job, gate deploy on it

databases/migrations/meta/_journal.json

@@ -0,0 +1,13 @@
+{
+  "version": "7",
+  "dialect": "postgresql",
+  "entries": [
+    {
+      "idx": 0,
+      "version": "7",
+      "when": 1777155028708,
+      "tag": "0000_square_jetstream",
+      "breakpoints": true
+    }
+  ]
+}